Background. Preliminary studies indicate that patient-centered care, characterized by incorporating the patient's experience of illness, the psychosocial context and shared decision-making, may reduce utilization while improving health status and satisfaction, especially among patients who present with unexplained somatic symptoms. These patients are common, incur high illness burden and cost, and are often dissatisfied with care. Patient-centeredness is mutable and reliably measurable. No published studies have assessed interactional factors associated with health care costs in this population of patients. Aims. To examine the relationship between measures of physicians' patient-centeredness and health care costs (total, inpatient, outpatient, testing and medication), health status and satisfaction; and to characterize features of patient-physician communication that contribute to lower health care costs. Methods: Multi-method study of 100 primary care physicians stratified by case-mix-adjusted total health care costs, and 50 patients/physician. Data: audiotapes of 2 SP visits simulating patients with unexplained somatic symptoms, questionnaires completed by patients and SPs. Measures: SP visits: Patient-Centered Communication Scoring Method and Thin Slice Analysis of non-verbal communication; Patients: SF-12, Patient Satisfaction Questionnaire; Health Status Change Question; SPs and patients: Health Care Climate Questionnaire and the Participatory DecisionMaking Scale; costs from a managed care database. Analyses: Qualitative coding/editing, and quasi-statistical analysis of physicians in highest and lowest cost quartiles. Regression analyses including SP and adjusted patient measures of patient-centeredness and case-mix adjusted costs. Significance: We will (1) address a deficiency in research on how patient-centered physician behaviors relate to health care costs (2 ) recognize modifiable factors in physician interaction style that can lead to decreased utilization, decreased costs, and recognition of emotional distress (4) guide randomized clinical trials of educational and quality improvement programs and (5) develop a new research methodology that provides an important link between cost data and behavioral and perceived measures of clinical encounter.